By using several reverse engineering tools and techniques, it is possible to extract business rules from the legacy source code that are easy to understand by the non-IT experts. These business rules can be used at different stages of system modernization. System maintainers can use the rules to locate in the code parts affected by a change in a rule. Business analysts can use those rules as means to aide understanding of the system at a business level. The extracted rules can serve as source of documentation and possible input for configuring a new system. This paper presents a novel approach for extracting business rules from legacy source code and application of the results at different stages of system modernization.